This application is directed to the subject matter than is generally related to the subject matter disclosed in the following U.S. applications: U.S. Ser. No. 07/588,990, filed Sep. 27, 1990; U.S. Ser. No. 07/667,301, filed Mar. 12, 1991; and U.S. Ser. No. 07/573,583, filed Aug. 28, 1990.
The present invention relates to a lead frame used, for example, as a component for producing a multi-core optical module.
A multi-core optical module, in which a plurality of optical operation elements (laser-diodes, photo diodes, etc.) are linked to a number of optical fibers, is used for building an optical communication system such as an optical local area network (LAN).
To produce such a multi-core optical module, electronic circuit elements are mounted on a substrate portion 1a of a lead frame (FIG. 1 or 2) and wires carrying optical connectors fixing optical operation elements are connected to the substrate portion. Subsequently, the lead frame is attached to a die mold, after which the multi-core optical module is produced by filling the die mold with resin.
However, when the optical operation elements including optical transmission circuits and optical receiving circuits are mounted on the single substrate portion 1a of the conventional lead frame 1 as shown in FIG. 1, signals of the optical transmission circuits may flow into the optical receiving circuits (cross talk) since they have a common ground, hence, erroneous operations are apt to occur. Furthermore, the substrate portion 1a has an unnecessarily large surface area, so that any thermal stress during, as well as after, the molding process may cause deterioration due to any cracks generated in a formed resin portion.
On the other hand, when the substrate portion 1a is divided into two parts in the conventional lead frame 1 as in FIG. 2, each being supported by three portions to electrically insulate the circuits, the substrate portion 1a is unstable before the molding step, so that wires connecting the optical operation element to the substrate portion 1a are apt to be damaged due to any resulting movement. Furthermore, the substrate portion 1a is apt to vibrate due to an ultrasonic frequency applied at the wire bonding, thus it is difficult to assure a sufficient strength of wire bonding.